During his Macworld Expo keynote address on Tuesday, Apple CEO Steve Jobs introduced the MacBook Air, a computer that the company billed as the world's thinnest notebook - small enough to fit inside an interoffice mailing envelope. It's priced starting at £1,199.

"We’ve built the world’s thinnest notebook - without sacrificing a full-size keyboard or a full-size 13-inch display," said Jobs. "When you first see MacBook Air, it's hard to believe it's a high-performance notebook with a full-size keyboard and display. But it is."

Sporting a silvery finish, the MacBook Air features a 13.3-inch LED-backlit widescreen display - it saves power and provides "instant on" response from the moment you turn it on, according to Jobs. The device has a slightly wedge-shaped profile that runs from 1.2 inches down to 0.8 inches high. It weighs about 3 pounds, and sports a thickness of 0.16-0.76 inches.

The MacBook Air also features a built-in iSight webcam and a full sized MacBook-style black keyboard. The keyboard is backlit, similar to MacBook Pros, and has an ambient light sensor that automatically adjusts brightness. The trackpad is also capable of recognizing multi-touch gestures, similar to using an iPhone or iPod touch.

The 1.6GHz MacBook Air features a 1.8 inch hard disk drive with 80GB of storage capacity standard. A 64GB solid-state disk (SSD) drive is also an option, though this is expensive (as Jobs admitted) - it costs an additional £639.

The laptop is powered by an Intel Core 2 Duo chip running at 1.6GHz, with 1.8GHz available as a £2,028 option. Jobs noted that Intel was willing to engineer a new version of the Core 2 Duo specifically to Apple's specifications - it's 60 per cent smaller than others. Intel CEO Paul Otellini joined Jobs on stage to present Apple's leader with a production sample of the chip.

Like the MacBook and the MacBook Pro, the MacBook Air features a MagSafe connector for power. It comes with a 45 watt power adaptor. A flip-down door on one side reveals a USB 2.0 connection, Micro-DVI (to connect an external display) and a headphone jack. The MacBook Air also includes 802.11n-based wireless networking support and Bluetooth 2.1 + EDR. The speakers are hidden underneath the keyboard.

Apple estimates that with wireless networking turned on, the MacBook Air can get about five hours of battery life.

No internal optical drive is included, but Apple will offer a £65 USB 2.0-based add-on. For users that opt not to get the optical drive, Apple is offering a new software feature on this machine called Remote Disk; it enables you to "borrow" the optical drive of another Mac or PC on the same network as the MacBook Air, to use for installing software, for example.

Apple's frequently been in the crosshairs of environmental group Greenpeace in recent years. Jobs offered information about the environmental goals behind the MacBook Air -- it has a fully recyclable aluminum case, and is "the first" to have a mercury-free display with arsenic-free glass. All the circuit boards are BFR-free and PVC-free, and the retail packaging uses 56 per cent less material than the MacBook packaging.